The Physics Question Bank

Film clips are a brilliant way to make GCSE physics feel less abstract. One great example is Dash from The Incredibles running at superhuman speed. A simple 100 m sprint can bring in speed, acceleration, kinetic energy, forces, Newton’s laws, air resistance and energy transfers.

The idea is simple: imagine Dash is running a 100 m race. Some of the physics is realistic, some of it is exaggerated, but that is what makes it useful. Pupils can calculate what would happen in the real world and then discuss where the film bends the rules.

Here are 10 GCSE physics questions based on Dash’s 100 m super sprint.

1. Dash runs 100 m in 12.5 s. Calculate his average speed.
2. In another race, Dash runs at an average speed of 16 m/s. Calculate the time taken to run 100 m.
3. Dash starts from rest and accelerates to 18 m/s in 3.0 s. Calculate his acceleration.
4. Dash has a mass of 40 kg. Calculate his kinetic energy when he is running at 20 m/s.
5. Dash increases his speed from 10 m/s to 20 m/s. Explain why his kinetic energy does not just double.
6. Dash pushes backwards on the ground with a force of 320 N. The ground pushes him forwards with the same size force. Name this law of motion.
7. Dash has a mass of 40 kg. A resultant force of 280 N acts on him. Calculate his acceleration.
8. At the end of the race, Dash slows from 20 m/s to 0 m/s in 2.5 s. Calculate his deceleration.
9. Dash skids to a stop after crossing the finish line. Describe the energy transfers that happen as he stops.
10. Dash runs so fast that air resistance becomes significant. Explain why there must be a resultant force forwards if Dash is still accelerating.

Answers

1. Speed = distance ÷ time
   Speed = 100 ÷ 12.5 = 8 m/s
2. Time = distance ÷ speed
   Time = 100 ÷ 16 = 6.25 s
3. Acceleration = change in velocity ÷ time
   Acceleration = 18 ÷ 3.0 = 6 m/s²
4. Kinetic energy = 0.5 × mass × speed²
   Kinetic energy = 0.5 × 40 × 20² = 8000 J
5. Kinetic energy depends on speed squared. If the speed doubles, the kinetic energy becomes four times bigger.
6. Newton’s third law.
7. Acceleration = force ÷ mass
   Acceleration = 280 ÷ 40 = 7 m/s²
8. Deceleration = change in velocity ÷ time
   Deceleration = 20 ÷ 2.5 = 8 m/s²
9. His kinetic energy is transferred mainly to thermal energy in his shoes, the ground and the air. Some energy is also transferred by sound.
10. If Dash is accelerating, the forward driving force must be bigger than the backward air resistance. This means there is a resultant force forwards.